I'm not an expert, but I looked into this once for a similar situation.
What I found was that the commercial value of the trees isn't necessarily what your deductible loss is.
The trees have no value unless bought or sold, so since they're in the ground, you can't just pull a number out of your rear end.

Since the trees are part of the property, you need to calculate the "basis" loss. This is based on the value of the property before and after the loss, and you would want appraisals from both before and after to back this up. Then, the amount you can deduct is also limited, and like the medical deduction, there is a minimum part that you cannot even deduct at all.